NREMT Emergency Medical Technician (EMT) Cognitive ExamPharmacologyHard
A 65-year-old male with a history of heart failure is experiencing acute pulmonary edema. His blood pressure is 150/90 mmHg, and he is severely dyspneic with crackles in all lung fields. You are considering administering sublingual nitroglycerin per protocol. What is the primary pharmacodynamic effect of nitroglycerin that directly alleviates pulmonary edema?
- AIncreased myocardial contractility.
- BDecreased preload through venous dilation.
- CBronchodilation.
- DIncreased systemic vascular resistance.
Show answer & explanationAnswer & explanation
Correct answer: B. Decreased preload through venous dilation.
Nitroglycerin causes significant venous dilation, leading to a decrease in venous return to the heart (preload). By reducing the amount of blood returning to the right side of the heart and subsequently the pulmonary circulation, it lessens the pressure in the pulmonary capillaries, thereby reducing fluid leakage into the lungs and alleviating pulmonary edema.
Why the other options are wrong
- A. Nitroglycerin primarily affects vascular smooth muscle, not directly increasing myocardial contractility; in fact, reduced preload can decrease it.
- C. Albuterol causes bronchodilation; nitroglycerin does not primarily act as a bronchodilator.
- D. Nitroglycerin causes vasodilation, which decreases, not increases, systemic vascular resistance (afterload).
Nitroglycerin in Pulmonary Edema
The therapeutic use of nitroglycerin to reduce fluid accumulation in the lungs (pulmonary edema), particularly in cardiac-related causes.
- Primary effect: Venodilation.
- Reduces preload (blood returning to heart).
- Decreases pulmonary capillary hydrostatic pressure.
- Alleviates fluid leakage into lung tissues.
Memory trick: Nitro opens veins wide, letting lung fluid subside.